add helpful guidance for mistyped `.exe.dev` domain attempts

Discord Message

Author: tekacs Channel: #feedback Link: https://discord.com/channels/1405685085923049482/1405686161791516873/1454575621144445162

Hullo! Maybe this has already been suggested, but my tired brain tried doing <myvm>.exe.dev every time I tried to access the web host side of things.

I recognize that for PSL/cookie/etc. reasons it's inappropriate to use that domain for user-generated content, but perhaps you might consider letting unused *.exe.dev show a page that says something akin to, "Did you mean .exe.xyz?", even without a real link or a noreferrer, to help folks along who make the same mistake?